Early warning mechanism for enhancing enterprise availability

ABSTRACT

A computer method for issuing an early warning includes determining, using change and test coverage and control flow and data flow analyses of a program, locations in the program at which to insert early warning (EW) code to monitor for an event. The program is instrumented with EW code which monitors for the event, by inserting EW code at the determined locations. Upon detecting the event, EW code performs an early action warning, or issues an early action. Early warnings are issued when an EW-instrumented block is reached. Issuance of an early warning action can be conditional upon execution of the program in a particular environment, such as a production environment. Issuance of an EW can also be conditional upon executing an untested block of code that was recently modified. The issuing of an early warning can include sending an email, writing into a log file, sending a message to a console, where the message causes the change of a human-perceptible characteristic, placing the program into a wait state, halting the program, sending an alarm to an operator, or triggering a failover. In some embodiments, EW code can be deactivated upon certain conditions. Issuance of an early warning can also occur upon an event such as the execution of a user-inserted assert or warning statement, or before a file is opened, wherein the EW issues if a null pointer about to be passed to a system function. In some embodiments, an EW will issue if the value of an argument to some function exceeds a predetermined range. In various embodiments, the EW code is placed in a loop, and issues an EW if the loop is executed more than a predetermined number of times, or the EW code issues an EW upon the execution of user-marked code, or the EW code issues an EW when the time duration between execution of two points in the program exceeds a predetermined value, or upon the detection of an untested configuration.

BACKGROUND OF THE INVENTION

With the proliferation of the internet and electronic commerce (“eCommerce”), businesses have begun to rely on the continuous operation of their computer systems. Even small disruptions of computer systems can have disastrous financial consequences as customers opt to go to other web sites or take their business elsewhere.

One reason that computer systems become unavailable is failure in the application or operating system code that runs on them. Failures in programs can occur for many reasons, including but not limited to, illegal operations such as dividing by zero, accessing invalid memory locations, going into an infinite loop, running out of memory, writing into memory that belongs to another user, accessing an invalid device, and so on. These problems are often due to program bugs.

Ayers, Agarwal and Schooler (hereafter “Ayers”), “A Method for Back Tracing Program Execution,” U.S. application Ser. No. 09/246,619, filed on Feb. 8, 1999 and incorporated by reference herein in its entirety, focuses on aiding rapid recovery in the face of a computer crash. When a computer runs an important aspect of a business, it is critical that the system be able to recover from the crash as quickly as possible, and that the cause of the crash be identified and fixed to prevent further crash occurrences, and even more important, to prevent the problem that caused the crash from causing other damage such as data corruption. Ayers discloses a method for recording a sequence of instructions executed during a production run of the program and outputting this sequence upon a crash.

Traceback technology is also important for purposes other then crash recovery, such as performance tuning and debugging, in which case some system event or program event or termination condition can trigger the writing out of an instruction trace.

The preferred method for traceback disclosed by Ayers is binary instrumentation in which code instrumentation is introduced in an executable. The instrumentation code writes out the trace.

Agarwal, “Test Protection, and Repair Through Binary-Code Augmentation,” U.S. Pat. No. 5,966,541, issued on Oct. 12,1999 and incorporated by reference herein in its entirety, discloses a method of binary instrumentation for aiding in testing programs through test coverage. The instrumentation marks instructions which were executed during a test run. Software test engineers or other testers could then write specific tests for the untested code, thereby improving overall test quality. One of the key aspects of the instrumentation technology is that it introduces virtually no overhead since it adds vew few extra instructions into the code directly, and does not involve expensive procedure calls. Improved testing also helps to discover and fix bugs, thereby resulting in higher availability for the system.

SUMMARY OF THE INVENTION

Traceback is a reactive tool. It promotes recovery when the program has crashed. But it does not usually warn of the possibility of a crash

The present invention, on the other hand, inserts binary instrumentation into a program which issues an “early warning” such as an email to an operator when the program enters a block of untested code which has been recently changed. Changed, untested codes are common causes of failures. Early warnings can also be issued upon other events that are likely to cause a failure.

Accordingly, a computer method for issuing an early warning includes determining, using a control flow graph representation of a program, locations in the program at which to insert EW code to monitor for an event. The program is instrumented with EW code which monitors for the event, by inserting EW code at the determined locations. Upon detecting the event, EW code performs an early action warning, or issues an early action.

In at least one embodiment, instrumenting the program is done by first injecting code coverage instrumentation into the program. Then, the code coverage-instrumented program is tested to provide coverage information. Finally, untested blocks are instrumented to perform an early warning action.

Instrumenting the program further comprises determining which program blocks in the program are changed relative to an earlier version of the program. Then, only untested blocks that are changed are instrumented to perform an early warning.

Early warnings in general are issued when an EW-instrumented block is reached. In one embodiment, the event is the reaching of program code which has changed relative to a prior version of the program.

Issuance of an early warning action can be conditional upon execution of the program in a particular environment, such as a production environment.

The issuing of an early warning can include, but is not limited to, sending an email to one or more people such as developers, testers, managers and/or operators, or to another computer system. The email can include information such as a traceback history.

The issuing of an early warning can also include, but is not limited to, writing an early warning log entry into a log file, which can be periodically checked by a human or by a processor. Furthermore, the log file or a portion thereof can be included in the email discussed above.

The issuing of an early warning can also include, but is not limited to, sending a message to a console, where the message causes the change of a human-perceptible characteristic. For example, the characteristic can be the color, visibility, shape, size or blinking state of an icon displayed on the console, or a combination thereof, where the icon is specific to the application. The characteristic can also be the sounding an audible alarm, or alternately, the turning off and on an audible alarm. This, of course, can be combined with the change of the icon's state. The message itself can be sent by various methods, including SNMP protocol traps.

The issuing of an early warning can also include, but is not limited to, placing the program into a wait state, halting the program, sending an alarm to an operator, or triggering a failover.

Furthermore, in some embodiments, EW code can be deactivated for a block after a predetermined number of early warnings have issued for the block. A table can be maintained, for example, to track the number of early warnings issued for each EW-instrumented block.

Alternatively, in some embodiments, EW code can be deactivated for the entire program, for example, after a predetermined number of early warning actions have been performed. This can be accomplished, for example, by checking for a predetermined condition before issuing the early warning, and issuing the early warning only if the predetermined condition is not true. Examples of predetermined conditions include, but are not limited to, a predetermined value stored in a known file or in an environmental variable.

Issuance of an early warning can also occur upon an event such as the execution of a user-inserted assert or warning statement, or before a file is opened, wherein the EW issues if a null pointer about to be passed to a system function. In some embodiments, an EW will issue if the value of an argument to some function exceeds a predetermined range.

In yet another embodiment, the EW code is placed in a loop, and issues an EW if the loop is executed more than a predetermined number of times.

In yet another embodiment, the EW code issues an EW upon the execution of user-marked code.

In another embodiment, the EW code issues an EW when the time duration between execution of two points in the program exceeds a predetermined value. The two points can be, for example, around a system call, a network request call, or a database interaction call.

In yet another embodiment, the EW code issues an EW upon the detection of an untested configuration. This can be implemented, for example, by maintaining a list of test configuration sets which have been tested. A configuration which does not match one of the listed test configuration sets is determined to be an untested configuration. A test configuration set can include, but is not limited to, a record of programs and/or processes and/or load modules that have been tested together during a test phase, a record of files which were opened during a test phase, or just those that were read from or just those that were written to, a record of system resources which were simultaneously open during a test phase. System resources can include, for example, a memory working set, the number of open communication sockets.

In yet another embodiment, the EW code issues an EW upon the creation of a helpdesk ticket.

In another embodiment, the EW code issues an EW before an exception handler passes control to an operating system.

In another embodiment, the EW code can be placed in an exception handler that is part of the executable, where the exception handler is registered with the operating system (OS). The exception handler is called by the OS when the OS determines that the executable has crashed. An example is the structured exception handler mechanism of Windows NT (tm).

The instrumentation can be of the source code, or the binary code, or can alternatively occur during linking.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 is a schematic diagram of an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an early warning.

FIGS. 3A-3E are schematic diagrams illustrating the behavior of various embodiments of the present invention.

FIG. 4 is a diagram of a table used in the implementation of the embodiment of FIG. 3B

FIG. 5 is a flowchart of the early warning instrumentation process of an embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a test-configuration-set embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram of an embodiment of the present invention. Generally, there is an earlier version of a computer program, say Version M 2A, and a later version of the computer program, say Version N 2B. For illustrative purposes, assume a control flow analysis reveals that Version M 2A comprises basic blocks A through F.

Version N 2B may have been derived from Version M 2A by inserting new lines of code, by changing lines of code, or by deleting lines of code. Use of a different compiler or assembler, or compiling with environmental variables set to different values from one compile to another, for example, can also result in different versions. In this example, new blocks B′ and E′ have been inserted after blocks B and E, respectively.

These two versions 2A, 2B are then compared by a changed code analyzer 4, which produces a list of code lines or blocks which have changed. Such an analyzer is described in Witchel, “Method for Determining the Degree to Which Changed Code Has Been Exercised,” Ser. No. 09/474,389, filed on the even day herewith and incorporated by reference herein in its entirety, which discloses a test coverage tool that performs “changed code coverage.” Lines of code that are changed are marked as changed. Furthermore, lines of code that are impacted by the changes are also marked as changed. In fact, additional statistics can be provided for changed and impacted lines. The changed code analyzer 4 can also compare two source files.

Impacted lines are determined from the changed lines by using control flow and data flow analyses. For example, if a variable's initialization is changed, then all instructions that use that variable in their calculations are impacted. Then, the new Version N 2B is instrumented to obtain coverage data by test instrumentor 10, resulting in version N* 2C. Version N* is tested and coverage data is produced. The lines of code that are executed in test 5 are marked as “T,” while those not executed in test 5 are marked as “{overscore (T)}.”

The illustrative output 6 of the changed code analyzer 4 demonstrates the changed code analysis function. For each basic block of the new version, i.e., Version N, a marking appears designating the changed (C) or not changed ({overscore (C)}) status. The output 8 of test 5 shows the marking of T or {overscore (T)}, as discussed above. Together, the C and T markings, 6, 8 respectively, are used in creating the EW instrumented version. Thus, for example, block B′ has the designation C {overscore (T)}, indicating that lines of code within block B′ have changed with respect to Version M, and have not been tested.

It is well-known that new changes are a common cause of failures. When new changes are untested, yet run in production, there is a high likelihood of failure. By determining, as described above, the lines or basic blocks of code that are changed and not tested, testers can focus their effort on testing these very blocks or lines, since they are likely to cause faults.

The present method and system provide early warnings based on this information. First, a control flow analyzer 17, which may be the same as or different from control flow analyzer 9, analyzes the program 2B to be instrumented. Then, using the resulting control flow analysis, and the C and T information, an early warning (hereafter “EW”) instrumentor 17 inserts EW code into those blocks which are determined to be changed and untested, such as block B′. An EW-instrumented version of the program N^(Δ) 2D is shown with basic block B′^(Δ), which is an EW-instrumented version of basic block B′.

Data flow analysis (not shown) can also be used to aid in the instrumentation.

Furthermore, EW code can be added either by source-level instrumentation or binary-level instrumentation. Other instrumentation methods such as link-time instrumentation can also be utilized.

FIG. 2 illustrates the operation of an EW agent, that is, the inserted code which issues EWs. Vertical line 2C represents the EW-instrumented program of FIG. 1, with only block B′^(Δ) being shown discretely. When EW-instrumented block B′^(Δ) is reached, the EW code, or agent, issues an early warning 14, which may include, for example, automatic generation and transmittal of an email 16 reporting the event, a log entry 18, an automated telephone call 20, or a message sent over the web to a support group. The message can include a trace record.

FIGS. 3A-3E illustrate various embodiments of EW behavior. Of course, these various embodiments can be combined in actual use. For example, in FIG. 3A, vertical line 50 represents an actual execution run of a program. Only the EW-instrumented blocks 51 are discretely depicted, each with a heavy line indicating the EW code. No scale is intended in FIGS. 3A-3E. That is, there could be zero lines of code between the instrumented blocks, a few lines, or many lines.

Note also that in each of FIGS. 3A-3E, the EW code, indicated by a heavy line, is shown at the beginning of each instrumented block for illustrative purposes. However, it should be understood that the instrumented EW code could in fact be inserted anywhere into a basic block, depending on the situation.

Finally, note that FIGS. 3A-3E represent execution runs, not source code. Thus, some blocks of code which appear in the source or binary code may not appear at all in the execution, while other blocks, for example, block 51, may execute several times in a single execution of the program.

FIG. 3A demonstrates the simple behavior wherein each EW agent 54 issues an early warning whenever the EW agent 54 is reached.

FIG. 3B demonstrates EW behavior for an alternate embodiment, in which, for performance or other reasons, after the first early warning on a given block, early warnings are turned off.

Here, the execution 55 comprises three executions of EW-instrumented block 56 and an execution of EW-instrumented block 58. Upon issuance of the first early warning from a particular EW-instrumented block 56, further issuance of EWs from that block 56 are disabled or inhibited. EWs can still be issued from other blocks when they are reached, however. Here, block 58 is not disabled, and issues its own EW when it is reached.

As shown in FIG. 4, this is accomplished, in one embodiment, by maintaining a table 90 of blocks instrumented with early warnings. When an early warning is issued, an indicator is set on the line corresponding to the block. Warnings are issued only after verifying that the indicator is 0.

For example, each entry in the table 90 of FIG. 4 has two fields: a block identifier field 91 and an issued indicator 93. Here, line 95 identifies block 310 as having an issued indicator which is set to 1, indicating that block 310 has issued an early warning. In this embodiment, further early warnings from block 310 are inhibitied.

Alternatively, EWs can be disabled after the Nth execution of an EW-instrumented block, for any number N, rather than after the first execution. In this case, the issued indicator field 93 of FIG. 4 can, for example, hold a count value of the number of issued early warnings.

FIG. 3C demonstrates yet another alternate EW behavior, in which early warnings can be shut off for an entire program. That is, if a program issues an EW, then further EWs from that program can be shut off. This can be implemented, for example, by checking, in the EW code, for some value, i.e., shut-off code, in a known file or an environment variable before issuing the early warning. Early warnings can then be turned off or inhibited by writing the shut off code into the particular file or environmental variable.

Here, for execution 60, a first (or Nth) EW disables or inhibits all further EWs. Thus, the first EW agent, in block 61 issues an EW and disables issuance of all further EWs. Later executions of block 61 do not issue an EW, nor does execution of a different EW-instrumented block 63.

Alternatively, EWs can be disabled for selected blocks.

FIG. 3D demonstrates yet another alternate EW behavior for execution 65. Here, a first EW agent, in block 66, records the time at which it is reached, say T₁. Later, an EW agent in block 68, noting the time of its own execution, say T₂, compares the duration between execution of the two blocks 66, 68, that is T₂−T₁, with some predetermined limit T_(L). If the time between execution of the two blocks 66, 68 exceeds the limit T_(L), an early warning is issued to indicate an unacceptable slowdown.

Such EW timer checks can be placed around system calls or calls that request network or database interaction. EWs can be fired off if one of these calls is inordinately slow.

Alternatively, an EW could issue if the time between execution of the two blocks is under some predetermined period.

FIG. 3E demonstrates yet another alternate EW behavior for an execution 70. Here, EWs are disabled until the Nth execution of an EW-instrumented block. For example, on the first two executions of block 71, no EW is issued. Only on the third execution of block 71 is an EW issued. Such conditional EW agents can be placed, for example, in loops, where they issue an EW if the loop is executed more than a given number of times. This mechanism catches infinite loops.

FIG. 5. is a flowchart 100 of one embodiment of the EW instrumentation process.

At Step 101, the difference between the executables of two versions is determined, for example, as described in Witchel, “Method for Determining the Degree to Which Changed Code Has Been Exercised,” Ser. No. 09/474,389, filed on the even day herewith and incorporated by reference herein in its entirety. Control and data flow analyses are performed, for example, as described in Schooler, “A Method for Determining Program Control Flow,” Ser. No. 09/210,138, filed on the even day herewith and incorporated by reference herein in its entirety, to aid in the determination of differences. The result is a list of lines of code that are changed and/or impacted, i.e., the “changed lines.”

At Step 103, those blocks that are changed are determined from the changed lines. See the Witchel application cited above. Any block with a changed line is a changed block.

At Step 105, all blocks are marked as untested.

At optional Step 107, instrumentation is injected into the executable to test for code coverage. The executable with code coverage instrumentation is then subjected to testing to provide coverage information. In other words, a determination can be made as to which blocks have been tested and which have not.

Then, at Step 109, the blocks that are changed and that have not been tested are further processed by the EW instrumentor 10 of FIG. 1. In this step, EW instrumentation is inserted to provide early warning into those blocks that are changed but not tested.

As discussed with respect to FIG. 2, one embodiment of an early warning action comprises causing one or more messages to be sent by email to one or more people, such as developers, tester, and/or managers, as appropriate.

Alternatively, or in addition, information is written into a log file, which is periodically checked.

Alternatively, an early warning message can be sent to a console, for example using SNMP protocol traps, and displayed. The early warning can optionally change a characteristic of an icon on the display to request that someone review the appropriate log file. Characteristics which can be changed include, but are not limited to: color, shape, size and blinking. Additionally, a sound or audible alarm, or other visual indicator, can be turned on, or alternately turned off and on.

For potentially catastrophic situations, a more strict action can be taken. For example, the application can be put into a wait state, or halted to prevent it from causing damage. An alarm can be sent to the operator, who can alert the appropriate operations personnel.

Further action of an early warning can include, for example, when the early warning code within an application suspects or detects that an application is about to fail or perform very poorly, sending a notification to a failover process so that a failover action can be initiated.

Failover is the mechanism by which an application is restarted on another computer or server when a computer, server or the application fails. The failover process optionally involves notifying message routers or some other higher level software process to send future transactions to the new location. The failover process also optionally involves notifying a higher level software system such as a transaction monitor that the application running on the current computer has failed.

One way that early warning code can suspect or detect that an application is about to fail or has failed, or is about to perform or is performing very poorly, is to place EW code at points in the program which are known to be reached only when the program is about to fail or has failed. In particular, early warning code can be placed just before an exception handler is reached, or alternatively at the start of the exception handler, so that the early warning code is run before the exception handler passes control to the operating system.

Many of the EW-instrumented locations discussed earlier are points in the program where the program is about to fail. One such example is where EW code discovers that a null pointer is about to be referenced as a valid memory location. In this case, the program is about to attempt to access memory through a null pointer, when a correct program would have a valid address in the pointer.

Early warning code is also placed in loops that are executed more than a preset number of times, as discussed with respect to FIG. 3E. This can signal imminent or in-progress poor performance.

Another way to signal poor performance is to measure the time between two program points in test, as discussed with respect to FIG. 3D. Between these program points might be a database access, or network access, or system call. The time interval can be measured by checking system time, which is available on most microprocessors, at two points in the program and taking the difference. If the EW code determines that the time interval falls outside acceptable bounds, established by the instrumentor 10, then an EW can issue that to cause a failover.

Early warnings can also be issued on other events in addition to the execution of untested code that is also changed.

For example, EWs can be issued on other events that can be monitored by instrumentation, such as the execution of a user-inserted assert or warning statement. First, a user can be allowed to intentionally place early warnings into a program.

Second, users commonly put “assert” statements into programs, such as:

assert(deposit_amount<10000)

In the C++ programming language, for example, executing such a statement in a program during the development process typically causes the program to halt if the condition within the parentheses is false. However, it is undesirable to ship code to customers in which asserts can be activated. For such production versions, asserts are typically defined to be null operations. Yet, it can be desirable, from the point of view of a customer running the program, or from the point of view of a software vendor supplying the program, to be able to know when these conditions occur.

User-inserted asserts or warnings typically produce either a determinable, or a predetermined sequence of instructions in the binary. That is, user-inserted asserts or warnings will produce a pattern of instructions in the binary that are recognizable by the EW instrumentor 19. Therefore, an embodiment of the present invention instruments assert or warning statements to issue an EW if the assert condition is in true or false, depending on the implementation.

In another embodiment, all file pointers are tested before the corresponding files are opened. An EW is issued if a null pointer is about to be passed to, for example, some system function.

In addition, EWs can be issued if some argument values exceed some customary ranges.

In yet another embodiment, a user is given the ability to mark code that should cause an early warning to be issued when it is executed. The EW instrumentor 19 recognizes such markings and instruments the code accordingly.

Another event upon which an EW can be issued is the creation of a helpdesk ticket.

Another embodiment maintains a record of programs or load modules that have been tested together during a test phase, as well as a record of the opened files and system resources during test. System resources include, but are not limited to, a memory working set, the number of communication sockets open, and so on. Each such set is called a “test-configuration-set.”

FIG. 6 illustrates the concept of a test-configuration EW system. Many test-configuration-sets 200 can be collected, and made available for reading by agents running in the application or in the system during production. For example, test-configuration-set #1 200-1 is defined by processes P1, P2, P3, P4 and P5 running, files F1 and F2 open, and system parameters SysParm1=X and SysParm2=Y for some values X and Y.

Similarly, test-configuration set #N 200-N is defined by processes P2, P3 and P6, files F1, F2 and F3, and system parameters SysParm1=X and SysParm2=W. Of course, in a real application, there could be many more test-configuration-sets and many more processes, files and system parameters than are shown here simply for illustrative purposes.

If the configuration running in production does not match one of the test configurations, then an EW is issued. In the Example of FIG. 6, the production configuration 202 currently has processes P2, P3 and P6 running, files F1, F2 and F3 open and system parameters SysParm1=X and SysParm2=W.

The matcher 204, which is simply code in the EW agent, looks for a match between the current production configuration 202 and any of the test-configuration sets 200. Here, the production configuration does not match either of the illustrated test-configuration-sets 200-1, 200-N. If no match is found with any test-configuration-set 200, as determined at Step 206, then at Step 208, an EW is issued. If a match is found, no EW issues.

Early warnings can also be accompanied by writing out a traceback history into a log file. Alternatively, a traceback history can be sent in an email along with the early warning message.

EWs can also be tied to the creation of a help desk ticket in systems such as Remedy (tm).

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 

What is claimed is:
 1. A computer method for issuing an early warning (EW), comprising: determining, using a control flow graph representation of a program, locations in the program at which to insert EW code to monitor for an event, including an untested configuration; maintaining a list of test configuration sets which have been tested, such that a configuration which does not match one of the listed test configuration sets is determined to be an untested configuration; instrumenting the program with EW code to monitor for the event, by inserting EW code at the determined locations; and upon detecting the event, performing, in the EW code, an early warning action.
 2. The method of claim 1, wherein instrumenting the program comprises: injecting code coverage instrumentation into the program; testing the code coverage-instrumented program to provide coverage information; and instrumenting untested blocks to perform an early warning action.
 3. The method of claim 1, further comprising: determining which program code has changed relative to a prior version of the program; and instrumenting the changed code such that the event is that the changed code is reached during execution of the program.
 4. The method of claim 1, wherein issuance of an early warning action is conditional upon execution of the program in a particular environment.
 5. The method of claim 4, wherein the particular environment is a production environment.
 6. The method of claim 1, wherein performing an early warning action comprises: sending an email comprising an early warning.
 7. The method of claim 6 wherein the email is sent to at least a developer.
 8. The method of claim 6 wherein the email is sent to at least a tester.
 9. The method of claim 6 wherein the email is sent to at least a manager.
 10. The method of claim 6 wherein the email is sent to at least an operator.
 11. The method of claim 6 wherein the email is sent to another computer system.
 12. The method of claim 6 wherein the email includes a traceback history.
 13. The method of claim 1, wherein an early warning action comprises sending a message over the web.
 14. The method of claim 13, where a receiver of the message is a person in a support group.
 15. The method of claim 13, wherein the message comprises a trace record.
 16. The method of claim 1, wherein performing an early warning action comprises: sending an message by telephone comprising an early warning.
 17. The method of claim 16, wherein the message is a voice message.
 18. The method of claim 1, wherein performing an early warning action comprises: writing an early warning log entry into a log file.
 19. The method of claim 18, further comprising: periodically checking the log file.
 20. The method of claim 19, wherein periodically checking the log file is performed by a human.
 21. The method of claim 19, wherein periodically checking the log file is performed by a processor.
 22. The method of claim 18, further comprising periodically emailing the log file.
 23. The method of claim 18, wherein performing an early warning action comprises: sending an email to at least one person, the email comprising an early warning.
 24. The method of claim 18, wherein performing an early warning action further comprises writing out a traceback history into the log file.
 25. The method of claim 1, wherein performing an early warning action comprises: sending a message to a console, said message causing a change of a human-perceptible characteristic.
 26. The method of claim 25, wherein SNMP protocol traps are used to send the message.
 27. The method of claim 25, wherein the characteristic is any or all of a color, visibility, shape, size or blinking state of an icon displayed on the console.
 28. The method of claim 27 wherein the icon is specific to an application.
 29. The method of claim 25, wherein the characteristic is any or all of sounding an audible alarm, or alternately turning off and on an audible alarm.
 30. The method of claim 1, wherein the early warning action comprises: placing the program into a wait state.
 31. The method of claim 1, wherein the early warning action comprises: halting the program.
 32. The method of claim 31, wherein the early warning action comprises: sending an alarm to an operator.
 33. The method of claim 1, wherein the early warning action comprises: sending an alarm to an operator.
 34. The method of claim 1, wherein the early warning action comprises: triggering a failover.
 35. The method of claim 1, further comprising: deactivating the EW code for a block after a predetermined number of early warning actions have been performed for the block.
 36. The method of claim 35, further comprising: maintaining a table of blocks with EW code to track the number of performed early warning actions for each EW-instrumented block.
 37. The method of claim 1, further comprising: deactivating the EW code for the entire program.
 38. The method of claim 37, wherein the EW code is deactivated after a predetermined number of early warning actions have been performed.
 39. The method of claim 37, wherein deactivating comprises: checking, in said means, for a predetermined condition before performing an early warning action; and performing the early warning action only if the predetermined condition is not true.
 40. The method of claim 39, wherein the predetermined condition comprises a predetermined value stored in a known file.
 41. The method of claim 39, wherein the predetermined condition comprises a predetermined value stored in an environmental variable.
 42. The method of claim 1 wherein the event comprises: executing a user-inserted assert or warning statement.
 43. The method of claim 1, further comprising: testing all file pointers before files are opened, wherein the event comprises a null pointer about to be passed to a system function.
 44. The method of claim 1, wherein the event comprises a value of an argument to some function exceeding a predetermined range.
 45. The method of claim 1, wherein the EW code is placed in a loop, wherein the event occurs if the loop is executed more than a predetermined number of iterations.
 46. The method of claim 1, wherein the event comprises execution of user-marked code.
 47. The method of claim 1, wherein the event is a time duration between execution of two points in the program exceeding a predetermined value.
 48. The method of claim 47, wherein the two points are around a system call.
 49. The method of claim 47, wherein the two points are around a network request call.
 50. The method of claim 47, wherein the two points are around a database interaction call.
 51. The method of claim 1, wherein the event comprises an occurrence of an untested configuration.
 52. The method of claim 51, wherein a test configuration set comprises a record of programs that have been tested together during a test phase.
 53. The method of claim 51, wherein a test configuration set comprises a record of load modules that have been tested together during a test phase.
 54. The method of claim 51, wherein a test configuration set comprises a record of files which were opened during a test phase.
 55. The method of claim 51, wherein a test configuration set comprises a record of files which were read during a test phase.
 56. The method of claim 51, wherein a test configuration set comprises a record of files which were written during a test phase.
 57. The method of claim 51, wherein a test configuration set comprises a record of system resources which were simultaneously open during a test phase.
 58. The method of claim 57, wherein a system resource comprises a memory working set.
 59. The method of claim 57, wherein a system resource is the number of open communication sockets.
 60. The method of claim 1, wherein the event comprises: creating a helpdesk ticket.
 61. The method of claim 1, further comprising: instrumenting source code of the program.
 62. The method of claim 1, further comprising: instrumenting binary code of the program.
 63. The method of claim 1, further comprising: instrumenting the program at link-time.
 64. The method of claim 1, wherein instrumenting the program comprises: inserting the EW code such that the EW code is run before an exception handler passes control to an operating system.
 65. The method of claim 1, wherein instrumenting the program comprises: inserting the EW code such that the EW code is run just prior to execution of an exception handler that signals a program crash.
 66. A computer method for issuing an early warning (EW), comprising: determining, using a control flow graph representation of a program, locations in the program at which to insert EW code to monitor for an event; determining which program blocks in the program are changed relative to an earlier version of the program; instrumenting changed blocks with EW code to monitor for the event, by inserting EW code at the determined locations; and upon detecting the event, performing, in the EW code, an early warning action.
 67. The method of claim 66, wherein the event is that an instrumented block is reached.
 68. A computer method for issuing an early warning (EW), comprising: executing at least one EW agent to monitor for untested lines of code; maintaining a list of test configuration sets which have been tested, such that lines of code which do not match one of the listed test configuration sets are determined to be the untested lines of code; upon detecting the untested lines of code, performing, in the agent, an early action warning.
 69. The method of claim 68, wherein a test configuration set comprises a record of programs that have been tested together during a test phase.
 70. The method of claim 68, wherein a test configuration set comprises a record of load modules that have been tested together during a test phase.
 71. The method of claim 68, wherein a test configuration set comprises a record of files which were simultaneously open during a test phase.
 72. The method of claim 68, wherein a test configuration set comprises a record of system resources which were simultaneously open during a test phase.
 73. The method of claim 72, wherein a system resource comprises a memory working set.
 74. The method of claim 72, wherein a system resource is the number of open communication sockets.
 75. A computer system for issuing an early warning (EW), comprising: a changed line analyzer for determining which lines of code of a program are changed; a control flow analyzer for producing a control flow representation of the program; a list of test configuration sets which have been tested, such that a configuration which does not match one of the listed test configuration sets is determined to be an untested configuration; and an instrumentor which inserts responsive to the changed lined analyzer and to the control flow analyzer, EW code to monitor for an event, including an untested configuration, wherein the EW code, upon detecting the event, issues an early warning.
 76. The computer system of claim 75, further comprising: a data flow analyzer for producing a data flow representation of the program, wherein the instrumentor is further responsive to the data flow analyzer.
 77. The computer system of claim 75, wherein the changed line analyzer further determines untested lines of code.
 78. The computer system of claim 75, wherein the changed line analyzer further determines lines of code which have executed during a production run.
 79. The computer system of claim 75, wherein issuing an early warning causes an email to be sent.
 80. The computer system of claim 75, wherein issuing an early warning causes a log entry to be written into a log file.
 81. The computer system of claim 75, wherein issuing an early warning causes a characteristic of an icon displayed on a console to change.
 82. The computer system of claim 75, wherein issuing an early warning causes an audible alarm to sound.
 83. The computer system of claim 75, wherein issuing an early warning causes the program to enter into a wait state.
 84. The computer system of claim 75, wherein issuing an early warning causes the program to halt.
 85. The computer system of claim 75, wherein issuing an early warning triggers a failover.
 86. The computer system of claim 75, wherein the EW code is deactivated for a block after a predetermined number of early warnings have issued for the block.
 87. The computer system of claim 75, wherein all early warnings are deactivated after a predetermined number of early warnings have issued.
 88. The computer system of claim 75, wherein the inserted EW code issues an EW when a null pointer is about to be passed to a system function.
 89. The computer system of claim 75, wherein the inserted EW code issues an EW when a value of an argument to some function exceeds a predetermined range.
 90. The computer system of claim 75, wherein the instrumentor inserts the EW code in a loop, wherein the EW code issues an EW if the loop is executed more than a predetermined number of times.
 91. The computer system of claim 75, wherein the inserted EW code issues an EW when a time duration between execution of two points in the program exceeds a predetermined value.
 92. The computer system of claim 75, wherein the inserted EW code issues an EW when an occurrence of an untested configuration is detected.
 93. The computer system of claim 75, wherein the instrumentor instruments source code of the program.
 94. The computer system claim 75, wherein the instrumentor instruments binary code of the program.
 95. The computer system of claim 75, wherein the instrumentor instruments the program at link-time.
 96. The computer system of claim 75, wherein the inserted EW code issues an EW before an exception handler passes control to an operating system.
 97. A computer program product for issuing an early warning (EW), the computer program product comprising a computer usable medium having computer readable code thereon, including code which: maintains a list of test configuration sets such that a configuration which does not match one of the listed test configuration sets is determined to be an untested configuration; determines a control flow representation of a program; and instruments the program with EW code to monitor for an event, including an untested configuration, responsive to the control flow representation, such that, upon detecting the event, the EW code issues an early action.
 98. The computer program product of claim 97, further including code which: determines which program blocks in the program are changed relative to an earlier version of the program, wherein only untested blocks that are changed are instrumented to perform an early warning.
 99. The computer program product of claim 97, further including code which: determines a data flow representation of the program; and instruments the program further responsive to the data flow representation.
 100. A computer memory configured for issuing an early warning (EW), comprising: a list of test configuration sets such that a configuration which does not match one of the listed test configuration sets is determined to be an untested configuration; a changed line analyzer for determining which lines of code of a program are changed; a control flow analyzer for producing a control flow representation of the program; and an instrumentor which inserts responsive to the changed line analyzer and to the control flow analyzer, EW code to monitor for an event, including an untested configuration, wherein the EW code, upon detecting the event, issues an early warning. 